Indirect epicardial targeting of left atrial tachycardia using Bachmann's bundle: A case report of successful ablation from pulmonary artery

Abstract

Successful rhythm control by standard endocardial methods may become quite challenging in some atrial tachycardia cases, very few of which may need extraordinarily different approaches after the initial failure of extensive endocardial ablation, such as epicardial ablation after subxiphoid puncture, or venous alcohol injection inside the vein of Marshall. With a good understanding of the structures nearby the LA, endocardially failed epicardial ATs can still be successfully ablated without directly entering the pericardial space.

Keywords: Bachmann's bundle; epicardial arrhythmia; indirect epicardial ablation; left atrial tachycardia; pulmonary artery.

FIGURE 1

Patient's initial electrocardiogram (ECG) (A‐left) and intracardiac electrogram (EGM) recording (B‐right). A. The ECG demonstrates features of an atrial arrhythmia with an irregular ventricular response. The negative P wave in lead I and the positive P wave in lead V1 suggest a left atrial tachycardia. B. An eccentric coronary sinus (CS) activation pattern (distal to proximal) was observed, indicating a left atrial origin. Therefore, left atrial mapping was planned as the initial approach.

FIGURE 2

Preablation comprehensive left atrial mapping (A–C). (A and B) In voltage mapping, electrical isolation of the ablation line around the pulmonary veins and posterior wall is evident. (C) Local activation time (LAT) mapping and histogram of the patient showing a macrorentrant AT with, CL 358 ms but still missing 35% of tachycardia cycle (TCL) over Bachmann's bundle.

FIGURE 3

(A) Fluoroscopic view of the ablation catheter positioned in the right anterior oblique (RAO) projection at the pulmonary artery bifurcation. (B) Contrast‐enhanced cardiac computed tomography image acquired prior to atrial tachycardia (AT) ablation, illustrating the close proximity between Bachmann's bundle (X), the right pulmonary artery (Y), and left atrial cavity (Z). (C and D) The bifurcation point was identified merely 7–8 mm above the initial endocardial termination site, where a faint far‐field electrogram (EGM) could still be discerned. On purpose of leveraging from this advantageous proximity, we administered radiofrequency (RF) energy at 40 W/30 mL irrigation for 2 min. The endocardial RF attempts prior to transitioning to the indirect epicardial route can be seen (D). (E) Endocardial far‐field signals (from right pulmonary artery) presumed to indicate an epicardial source are observed in the PNT 7–8 bipolar channel. (F) Patient's postprocedure ECG; it was observed that sinus rhythm was restored and partial Bachmann's bundle block (Interatrial block) has developed: Inferior limb leads on the ECG show notching and a prolonged P wave duration (>120 milliseconds), which are indicative of partial interatrial block. If the prolonged P wave is accompanied by a biphasic morphology in the inferior leads, this is termed advanced or complete interatrial block. Postprocedure ECG of this patient reveals partial negativity in the terminal deflection of the P wave and intermittent notching, suggesting a delay in interatrial conduction or the development of an advanced interatrial block.